Laser cladding silt-abrasion-resistant gradient coating powder as well as forming process and application of laser cladding silt-abrasion-resistant gradient coating powder

Abstract

The invention discloses laser cladding silt-abrasion-resistant gradient coating powder and a forming process and application, the laser cladding silt-abrasion-resistant gradient coating powder comprises bottom layer powder, middle layer powder and surface layer powder, the types of elements in all the layers of powder are the same, and the proportions of all the elements in all the layers of powder are changed in a gradient mode from the bottom layer to the surface layer according to the atomic percent; wherein the bottom layer powder is prepared from 25%-35% of WC, 40%-50% of Ni, 15%-25% of Cu and 0.5%-3% of NbC; the middle layer powder comprises 45%-55% of WC, 20%-40% of Ni, 5%-15% of Cu and 0.5%-3% of NbC; the surface layer powder comprises 65%-75% of WC, 10%-30% of Ni, 3%-10% of Cu and 0.5%-3% of NbC. After being formed by adopting a laser cladding process, the powder has the performance characteristics of low crack sensitivity, high toughness, high corrosion resistance, high hardness and the like, and is suitable for hydraulic equipment in a high-silt-content, high-speed and high-impact-force overflowing environment.

Description

Technical Field

[0001] The present invention relates to the technical field of surface coating strengthening of flow components of hydraulic turbines, and particularly relates to a laser cladding anti-silt erosion gradient coating powder, a forming process and an application thereof. Background Art

[0002] The anti-abrasion problem of hydraulic equipment components in high-silt-content, high-flow-rate, and high-impact-force flow environments needs to be solved urgently. Especially for the anti-silt erosion problem of the flow components of high-head and large-capacity hydraulic turbines, the overhaul period of the hydraulic turbines is very short, and major overhauls are required every 1 to 2 years, which greatly limits the power generation efficiency of hydropower stations, increases a large amount of time and economic costs, and also hinders the development process of high-head hydraulic resources in the country.

[0003] There are two common anti-abrasion methods for the flow surfaces of hydraulic machinery parts. One is to prepare a high-proportion hard-phase alloy coating through supersonic thermal spraying. However, the coating prepared by supersonic thermal spraying has a low bonding strength with the substrate, generally about 70 MPa, and the coating is thin and brittle, and it is easy to crack and peel under the impact of high-impact-force silt, so it cannot solve the abrasion problem of hydraulic equipment components in high-silt-content, high-speed, and high-impact-force flow environments. The other is to prepare an alloy cladding layer through laser cladding technology. Because the laser cladding coating and the substrate are metallurgically bonded, the bonding strength between the coating and the substrate can exceed 300 MPa, and it can withstand the impact of high-impact-force silt.

[0004] However, when laser cladding a high-proportion hard-phase alloy coating, the coating often cracks due to excessive internal stress under high particle impact force. This problem makes the current laser cladding technology only applicable to preparing coatings with a low content of hard phases, which greatly limits the anti-abrasion performance and engineering application of laser cladding coatings. Therefore, solving the problem of high crack tendency of laser cladding high-proportion hard-phase alloy coatings is an effective way to solve the abrasion problem of hydraulic equipment components in high-silt-content, high-speed, and high-impact-force flow environments.

[0005] Chinese Patent Document CN115537807A, Publication (Announcement) Date: December 30, 2022, discloses an impact-resistant, wear-resistant and corrosion-resistant high-entropy alloy-ceramic composite coating, its preparation method and application, belonging to the field of coating technology. The composite coating includes a first coating, a second coating and a third coating from the inside to the outside; the raw materials for preparing each coating independently include FeCoNiCr high-entropy alloy and ceramic particles; in atomic percentage, the high-entropy alloy contains 22-28% of Fe, 22-28% of Co, 22-28% of Ni and 22-28% of Cr; the ceramic particles include at least one of WC, Cr3C2 and Al2O3; the particle size of the ceramic particles is 45-85 μm; the amounts of ceramic particles contained in the raw materials for preparing the three-layer coating are 5-15%, 20-30% and 50-60% in sequence; the thickness ratio of the three-layer coating is 1:0.8-0.9:0.6-0.7. Its characteristics are: this composite coating has excellent impact resistance, wear and corrosion resistance at the same time; its deficiencies are: this document solves the problems of corrosion and wear, rather than solving the erosion problem of high-impact sediment on the surface of flow components in this application. In addition, the composition of its coating is also different from that of this application.

[0006] In addition, Chinese Patent Document CN116555758A, Publication (Announcement) Date: November 14, 2023, discloses a cermet gradient coating, its preparation method and application. The cermet gradient coating includes a first gradient layer and a second gradient layer that are sequentially laser-clad on the surface of a copper substrate; the raw material components of the first gradient layer, calculated by weight percentage, include: Ni60 65-80wt%, WC 0-15wt%, Cu 8-12wt% and Ni 8-12wt%; the raw material components of the second gradient layer, calculated by weight percentage, include: Ni60 80-90wt%, WC 10-20wt%. Its advantages are: it improves the hardness and wear resistance of the coating; its deficiencies are: this document solves the wear problem. To solve the wear problem, as long as some particles, namely WC particles, are in the clad coating, the wear performance of the entire surface can be significantly improved. The WC added in this document is very little and is unevenly distributed in the structure, so it cannot solve the erosion problem. To improve the erosion performance, the performance of each point on the surface of the substrate needs to be high and it cannot peel off. Summary of the Invention

[0007] To solve the current existing technical problems, the main purpose of the present invention is to provide a laser-clad anti-sediment erosion gradient coating powder, its forming process and application, so as to solve the anti-erosion problem of hydraulic equipment parts in a high-sediment-content, high-speed and high-impact flow environment.

[0008] To overcome the problems existing in the prior art, the technical solution adopted by the present invention is as follows: A laser cladding anti-sediment abrasion gradient coating powder, comprising: a bottom layer powder, an intermediate layer powder, and a surface layer powder. The types of elements in each layer of powder are the same. In atomic percentage, from the bottom layer to the surface layer, the proportions of each element in each layer of powder change in a gradient manner; Among them, the bottom layer powder comprises: WC: 25-35%, Ni: 40-50%, Cu: 15-25%, NbC: 0.5-3%; The intermediate layer powder comprises: WC: 45-55%, Ni: 20-40%, Cu: 5-15%, NbC: 0.5-3%; The surface layer powder comprises: WC: 65-75%, Ni: 10-30%, Cu: 3-10%, NbC: 0.5-3%.

[0009] The bottom layer powder comprises: WC: 30%, Ni: 46%, Cu: 22%, NbC: 2%; The intermediate layer powder comprises: WC: 50%, Ni: 35%, Cu: 14%, NbC: 1%; The surface layer powder comprises: WC: 70%, Ni: 20%, Cu: 9.5%, NbC: 0.5%.

[0010] The bottom layer powder comprises: WC: 28%, Ni: 50%, Cu: 20%, NbC: 2%; The intermediate layer powder comprises: WC: 45%, Ni: 40%, Cu: 13%, NbC: 2%; The surface layer powder comprises: WC: 65%, Ni: 26%, Cu: 8%, NbC: 1%.

[0011] The bottom layer powder comprises: WC: 35%, Ni: 45%, Cu: 18.5%, NbC: 1.5%; The intermediate layer powder comprises: WC: 55%, Ni: 35%, Cu: 9%, NbC: 1%; The surface layer powder comprises: WC: 75%, Ni: 18%, Cu: 6.5%, NbC: 0.5%.

[0012] The bottom layer powder, the intermediate layer powder, and the surface layer powder are obtained by a gas atomization powder making method.

[0013] The particle sizes of the bottom layer powder, the intermediate layer powder, and the surface layer powder are 40-150 μm.

[0014] The forming process using the laser cladding anti-sediment abrasion gradient coating powder comprises the following steps: S1. Obtain dry bottom layer powder, intermediate layer powder, and surface layer powder; S2. Remove the oil stain on the substrate surface, then adjust the distance between the laser cladding processing head and the substrate to adjust the laser defocus amount, and quickly scan the substrate with the defocused light spot to preheat the substrate surface; S3. Perform laser cladding operation. The laser cladding process parameters are: laser power 1.2 - 3.8 KW, scanning speed 5 - 12 mm / s, spot overlap rate 30 - 70%, powder feeding rate 20 - 120 g / min, spot diameter 4 - 10 mm; For the bottom layer powder, intermediate layer powder and surface layer powder respectively, select three suitable laser cladding process parameters, and successively perform the laser cladding process of the bottom layer powder, intermediate layer powder and surface layer powder on the substrate surface.

[0015] The substrate is 04Cr13Ni5Mo steel. When preheating the substrate surface, the preheating temperature is 150 - 350 °C.

[0016] During the laser cladding process, the thickness of the bottom layer powder cladding layer is controlled at 1 - 1.5 mm, the thickness of the intermediate layer powder cladding layer is controlled at 0.6 - 0.9 mm, and the thickness of the surface layer powder cladding layer is controlled at 0.4 - 0.6 mm.

[0017] Apply the laser cladding anti - sediment abrasion gradient coating powder to the flow - through components of the hydropower unit.

[0018] The present invention has the following beneficial effects: The present invention innovatively designs in two aspects of powder formula and laser cladding process to solve the problem of anti - sediment abrasion of hydraulic equipment in the high - sediment - content, high - speed, high - impact flow - through environment.

[0019] 1. According to the reactions between elements, the impact resistance of materials and the characteristics of laser cladding technology, an innovative WCNiCuNbC element formula is designed, and three proportional element formulas are designed to be used in combination. After the three - formula powders are formed by laser cladding process, they have the performance characteristics of low crack sensitivity, high toughness, high corrosion resistance, high hardness, etc., and are suitable for hydraulic equipment in the high - sediment - content, high - speed, high - impact flow - through environment.

[0020] 2. By using laser cladding technology to prepare an anti-sediment abrasion gradient coating, the problems of brittleness, poor impact resistance, and easy crack and fracture in the coating during the preparation of a high-proportion hard-phase coating by laser cladding are solved. The main reasons for the above problems in the coating are the technical characteristics of rapid heating and cooling in laser cladding and the large differences in physical and chemical properties between the high-proportion hard-phase coating and the substrate, such as elastic strain, yield strength, and coefficient of thermal expansion. The present invention mainly prepares a three-layer coating of the same element through three powder formulations with a gradient change in WC content. The same element can make the transition of the structure and organization of the three-layer coating more uniform, the combination more compact, and the transition of physical and chemical properties more gentle, effectively solving the problem that when a high-proportion WC coating is subjected to a high impact force, due to the large difference in material properties from the substrate material and the mismatch of stress and strain with the substrate material, cracks are likely to occur in the coating.

[0021] 3. The bonding strength between the coating of the present invention and the substrate is ≥350 MPa, and it does not fall off under the impact of high sediment impact force. The comprehensive anti-sediment abrasion performance is 7-8 times that of 04Cr13Ni5Mo steel, which is a typical steel for hydraulic flow equipment. Moreover, compared with other preparation methods of high-proportion hard-phase coatings, such as supersonic thermal spraying WC coatings, the coating thickness is generally 0.25-0.4 mm. The coating of the present invention can range from 0.5 mm to several millimeters in thickness, and even centimeter-level thickness, which can greatly increase the service life of hydraulic flow equipment.

[0022] 4. NbC is added to the coating powder of the present invention, which can inhibit the growth of WC grains and enhance the toughening of the coating after laser cladding. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0024] Figure 1 It is a schematic diagram of the forming process of the laser cladding anti-sediment abrasion gradient coating powder of the present invention Reference numerals: 1. Substrate, 2. Bottom powder cladding layer, 3. Intermediate powder cladding layer, 4. Surface powder cladding layer, 5. Laser cladding processing head. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] In order to make the above objects, features, and advantages of the present invention more obvious and understandable, the following will make a detailed description of the specific embodiments of the present invention in conjunction with the drawings of the specification.

[0026] In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, the present invention may be practiced in other ways different from those described herein. Those skilled in the art can make similar generalizations without departing from the spirit of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0027] Secondly, as used herein, "this embodiment" or "embodiment" refers to specific features, structures, or characteristics that may be included in at least one implementation of the present invention.

[0028] Furthermore, the present invention is described in detail in conjunction with schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views showing the device structure are enlarged locally in a non-general proportion, and the schematic diagrams are only examples and should not limit the scope of protection of the present invention herein. In addition, in actual production, three-dimensional spatial dimensions including length, width, and depth should be included.

[0029] Embodiment 1: This embodiment provides a laser cladding anti-sediment abrasion gradient coating powder, including: bottom layer powder, intermediate layer powder, and surface layer powder. The types of elements in each layer of powder are the same. In atomic percentage, from the bottom layer to the surface layer, the proportions of each element in each layer of powder change in a gradient manner; Among them, the bottom layer powder includes: WC: 25 - 35%, Ni: 40 - 50%, Cu: 15 - 25%, NbC: 0.5 - 3%; The intermediate layer powder includes: WC: 45 - 55%, Ni: 20 - 40%, Cu: 5 - 15%, NbC: 0.5 - 3%; The surface layer powder includes: WC: 65 - 75%, Ni: 10 - 30%, Cu: 3 - 10%, NbC: 0.5 - 3%.

[0030] WC is tungsten carbide powder, Ni is nickel powder, Cu is copper powder, and NbC is niobium carbide powder.

[0031] According to the reactions between elements, the impact resistance of materials, and the characteristics of laser cladding technology, an innovative design of the WCNiCuNbC element formula is made, and three proportional element formulas are designed to be used in combination. After the three formulas of powder are formed by the laser cladding process, they have performance characteristics such as low crack sensitivity, high toughness, high corrosion resistance, and high hardness, and are suitable for hydraulic equipment in high-sediment-content, high-speed, and high-impact flow environments.

[0032] NbC is added to the coating powder, which can inhibit the growth of WC grains and enhance the toughening of the coating after laser cladding.

[0033] Specifically, in this embodiment, the substrate 1 is made of 04Cr13Ni5Mo steel commonly used in hydraulic machinery. In atomic percentage, the bottom layer powder includes: WC: 30%, Ni: 46%, Cu: 22%, NbC: 2%. The intermediate layer powder includes: WC: 50%, Ni: 35%, Cu: 14%, NbC: 1%. The surface layer powder includes: WC: 70%, Ni: 20%, Cu: 9.5%, NbC: 0.5%.

[0034] Further, the powder preparation method adopts the method of aerosol alloying. The powder particle size is required to be 70 - 100 μm, and powder particles with more uniform and tighter wrapping of the hard phase can be obtained, which is adapted to the technical characteristics of rapid heating and cooling of laser cladding and is suitable for preparing coatings by laser cladding technology.

[0035] Embodiment 2: Adopt the forming process of the laser cladding anti - sediment abrasion gradient coating powder of Embodiment 1 of the present invention, including the following steps: (1) Put the three kinds of formulated powders into an incubator and dry them at 70 - 80 °C for 2 - 3 hours; (2) Clean the surface of the substrate 1 with organic solvents such as anhydrous alcohol and acetone to remove the oil stain on the surface of the substrate 1. Then adjust the distance between the laser cladding processing head 5 and the substrate 1 to adjust the laser defocus amount, and preheat the surface of the substrate 1 by quickly scanning the substrate 1 with the defocused light spot. The preheating temperature is about 250 °C; (3) Adjust the laser cladding process parameters as follows: laser power 2.8 KW, scanning speed 10 mm / s, light spot overlapping rate 50%, powder feeding rate 100 g / min, light spot diameter 6 mm, and carry out the laser cladding preparation process of the bottom layer powder cladding layer 2; (4) Adjust the laser cladding process parameters as follows: laser power 3.2 KW, scanning speed 8 mm / s, light spot overlapping rate 55%, powder feeding rate 65 g / min, light spot diameter 6 mm, and carry out the laser cladding preparation process of the intermediate layer powder cladding layer 3; (5) Adjust the laser cladding process parameters as follows: laser power 3.6 KW, scanning speed 6 mm / s, light spot overlapping rate 65%, powder feeding rate 45 g / min, light spot diameter 6 mm, and carry out the laser cladding process of the surface layer powder cladding layer 4; (6) Complete the preparation of the laser cladding anti - sediment abrasion gradient coating, and then turn off the powder feeding, laser, gas supply, cooling, and power supply.

[0036] Embodiment 1 of the present invention is suitable for hydraulic flow components in water environments with high sediment content, high speed, high impact force, and an average sand particle size of about 85 μm.

[0037] Embodiment 3: In this embodiment, the substrate 1 is made of 04Cr13Ni5Mo steel commonly used in hydraulic machinery. By atomic percentage: The bottom layer powder includes: WC: 28%, Ni: 50%, Cu: 20%, NbC: 2%; The intermediate layer powder includes: WC: 45%, Ni: 40%, Cu: 13%, NbC: 2%; The surface layer powder includes: WC: 65%, Ni: 26%, Cu: 8%, NbC: 1%.

[0038] Furthermore, the powder preparation method adopts the method of aerosol alloying. The powder particle size is required to be 40 - 70μm, and powder particles with more uniform and tighter wrapping of the hard phase can be obtained, which is adapted to the technical characteristics of rapid heating and cooling in laser cladding and is suitable for preparing coatings by laser cladding technology.

[0039] Example 4: Adopt the forming process of the laser cladding anti-sediment abrasion gradient coating powder of Embodiment 3 of the present invention, including the following steps: (1) Put the three kinds of formulated powders into an incubator and dry them at 70 - 80°C for 2 - 3 hours; (2) Clean the surface of the substrate 1 with organic solvents such as anhydrous alcohol and acetone to remove the oil stain on the surface of the substrate 1. Then adjust the distance between the laser cladding processing head 5 and the substrate 1 to adjust the laser defocus amount, and preheat the surface of the substrate 1 by quickly scanning the substrate 1 with the defocused light spot. The preheating temperature is about 250°C; (3) Adjust the laser cladding process parameters as follows: laser power 2.4KW, scanning speed 11mm / s, spot overlap rate 50%, powder feeding rate 110g / min, spot diameter 7mm, and carry out the laser cladding preparation process of the bottom layer powder cladding layer 2; (4) Adjust the laser cladding process parameters as follows: laser power 2.8KW, scanning speed 9mm / s, spot overlap rate 55%, powder feeding rate 75g / min, spot diameter 7mm, and carry out the laser cladding preparation process of the intermediate layer powder cladding layer 3; (5) Adjust the laser cladding process parameters as follows: laser power 3.2KW, scanning speed 7mm / s, spot overlap rate 60%, powder feeding rate 55g / min, spot diameter 7mm, and carry out the laser cladding process of the surface layer powder cladding layer 4; (6) Complete the preparation of the anti-sediment abrasion WC gradient change laser cladding coating, and then turn off the powder feeding, laser, gas supply, cooling, and power supply.

[0040] Embodiment 3 of the present invention is suitable for application to hydraulic flow components in water environments with high sediment content, high speed, high impact force, and an average sand grain size of about 135μm.

[0041] Example 5: In this embodiment, the substrate 1 is made of 04Cr13Ni5Mo steel commonly used in hydraulic machinery. In atomic percentage: The bottom layer powder includes: WC: 35%, Ni: 45%, Cu: 18.5%, NbC: 1.5%; The intermediate layer powder includes: WC: 55%, Ni: 35%, Cu: 9%, NbC: 1%; The surface layer powder includes: WC: 75%, Ni: 18%, Cu: 6.5%, NbC: 0.5%.

[0042] Furthermore, the powder preparation method adopts the aerosol alloying method. The powder particle size is required to be 100 - 130 μm, and powder particles with more uniform and tighter wrapping of the hard phase can be obtained, which is adapted to the technical characteristics of rapid heating and rapid cooling of laser cladding and is suitable for preparing coatings by laser cladding technology.

[0043] Example 6: Adopt the forming process of the laser cladding anti - sediment abrasion gradient coating powder of Embodiment 5 of the present invention, including the following steps: (1) Put the three - formula powders into an incubator and dry them at 70 - 80 °C for 3 hours; (2) Clean the surface of the substrate 1 with organic solvents such as anhydrous alcohol and acetone to remove the oil stain on the surface of the substrate 1. Then adjust the distance between the laser cladding processing head 5 and the substrate 1 to adjust the laser defocus amount, and pre - heat the surface of the substrate 1 by quickly scanning the substrate 1 with the defocused light spot. The pre - heating temperature is about 250 °C; (3) Adjust the laser cladding process parameters as follows: laser power 3.2 KW, scanning speed 8 mm / s, spot overlap rate 60%, powder feeding rate 55 g / min, spot diameter 5 mm, and carry out the laser cladding preparation process of the bottom layer powder cladding layer 2; (4) Adjust the laser cladding process parameters as follows: laser power 3.5 KW, scanning speed 6 mm / s, spot overlap rate 65%, powder feeding rate 45 g / min, spot diameter 5 mm, and carry out the laser cladding preparation process of the intermediate layer powder cladding layer 3; (5) Adjust the laser cladding process parameters as follows: laser power 3.8 KW, scanning speed 5 mm / s, spot overlap rate 70%, powder feeding rate 35 g / min, spot diameter 5 mm, and carry out the laser cladding process of the surface layer powder cladding layer 4; (6) Complete the preparation of the anti - sediment abrasion WC gradient - change laser cladding coating, and then turn off the powder feeding, laser, gas supply, cooling, and power supply.

[0044] Embodiment 5 of the present invention is suitable for application to hydraulic flow components in water environments with high sediment content, high speed, high impact force, and an average sand particle size of approximately 35 μm.

[0045] Example 7: Based on Examples 1 - 6, during the laser cladding process, the thickness of the bottom powder cladding layer 2 is controlled within 1 - 1.5 mm, the thickness of the intermediate powder cladding layer 3 is controlled within 0.6 - 0.9 mm, and the thickness of the surface powder cladding layer 4 is controlled within 0.4 - 0.6 mm. The laser cladding anti - sediment abrasion gradient coating powder is applied to the flow - through components of the hydro - generator set, especially suitable for application on the flow - through components in an environment with high flow velocity, high impact force, and high sediment abrasion.

[0046] It should be understood that during the development of any actual implementation, in any engineering or design project, a large number of specific implementation decisions can be made. Such development efforts may be complex and time - consuming, but for those of ordinary skill in the art who benefit from this disclosure, without excessive experimentation, the development efforts will be a routine task of design, manufacturing, and production.

[0047] It should be noted that the above examples are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A laser cladding anti-sand abrasion gradient coating powder, characterized in that: include: The bottom layer powder, the middle layer powder and the surface layer powder have the same element types in each layer of powder. In terms of atomic percentage, the proportion of each element in each layer of powder changes gradually from the bottom layer to the surface layer. Among them, the bottom powder includes: WC: 25-35%, Ni: 40-50%, Cu: 15-25%, NbC: 0.5-3%; The intermediate layer powder includes: WC: 45-55%, Ni: 20-40%, Cu: 5-15%, NbC: 0.5-3%; The surface layer powder includes: WC: 65-75%, Ni: 10-30%, Cu: 3-10%, NbC: 0.5-3%.

2. The laser cladding anti-sand abrasion gradient coating powder according to claim 1 is characterized in that: The bottom layer powder includes: WC: 30%, Ni: 46%, Cu: 22%, NbC: 2%; The intermediate layer powder includes: WC: 50%, Ni: 35%, Cu: 14%, NbC: 1%; The surface layer powder includes: WC: 70%, Ni: 20%, Cu: 9.5%, NbC: 0.5%.

3. The laser cladding anti-sand abrasion gradient coating powder according to claim 1 is characterized in that: The bottom layer powder includes: WC: 28%, Ni: 50%, Cu: 20%, NbC: 2%; The intermediate layer powder includes: WC: 45%, Ni: 40%, Cu: 13%, NbC: 2%; The surface layer powder includes: WC: 65%, Ni: 26%, Cu: 8%, NbC: 1%.

4. The laser cladding anti-sand abrasion gradient coating powder according to claim 1 is characterized in that: The bottom layer powder includes: WC: 35%, Ni: 45%, Cu: 18.5%, NbC: 1.5%; The intermediate layer powder includes: WC: 55%, Ni: 35%, Cu: 9%, NbC: 1%; The surface layer powder includes: WC: 75%, Ni: 18%, Cu: 6.5%, NbC: 0.5%.

5. The laser cladding anti-sand abrasion gradient coating powder according to any one of claims 1 to 4, characterized in that: The bottom layer powder, the middle layer powder and the surface layer powder are obtained by adopting an aerosol powder making method.

6. The laser cladding anti-sand abrasion gradient coating powder according to any one of claims 1 to 4, characterized in that: The particle sizes of the bottom layer powder, the middle layer powder and the surface layer powder are 40-150 μm.

7. The forming process of the laser cladding anti-sand abrasion gradient coating powder according to any one of claims 1 to 4 is characterized in that: The following steps are involved: S1, obtaining dry bottom layer powder, middle layer powder and surface layer powder; S2, remove the oil stains on the substrate surface, then adjust the distance between the laser cladding processing head and the substrate to adjust the laser defocus amount, and quickly scan the substrate with the defocused spot to preheat the substrate surface; S3, laser cladding operation is performed, and the laser cladding process parameters are: laser power 1.2-3.8KW, scanning speed 5-12mm / s, spot overlap rate 30-70%, powder feeding rate 20-120g / min, spot diameter, 4-10mm; Three suitable laser cladding process parameters are selected for the bottom layer powder, the middle layer powder and the surface layer powder respectively, and the laser cladding processes of the bottom layer powder, the middle layer powder and the surface layer powder are carried out on the surface of the substrate in sequence.

8. The molding process according to claim 7, characterized in that: The substrate is made of 04Cr13Ni5Mo steel. When the surface of the substrate is preheated, the preheating temperature is between 150°C and 350°C.

9. The molding process according to claim 7, characterized in that: During the laser cladding process, the thickness of the bottom powder cladding layer is controlled at 1-1.5 mm, the thickness of the middle powder cladding layer is controlled at 0.6-0.9 mm, and the thickness of the surface powder cladding layer is controlled at 0.4-0.6 mm.

10. Use of the laser cladding anti-silt abrasion gradient coating powder according to any one of claims 1 to 4 on flow-through components of a hydropower unit.

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